drivers/usbdev/cdcncm: send TX immediately, not after a tick-quantized delay cdcncm_send() defers each transmit with MSEC2TICK(CDCNCM_DGRAM_COMBINE_PERIOD) (1 ms). MSEC2TICK() rounds up to the system tick, so at the default 100 Hz tick the "1 ms" coalescing window becomes a full 10 ms tick (10-20 ms with phase), adding that latency to every single-datagram reply (ICMP echo, TCP ACK, one-MSS HTTP segment) and dominating the CDC-NCM round-trip time. The window only coalesces datagrams appended within the same synchronous TX burst (already queued before the worker runs), so an inter-burst delay adds latency without batching benefit in the common case. Fire the transmit worker immediately (delay 0); within-burst coalescing is preserved. On RP2350 (Pico 2 W) USB-NIC at 100 Hz tick: ping RTT 21.7 -> 2.8 ms, a 257 KB HTTP download 5.79 -> 0.92 s (44.5 -> 279 KB/s). Signed-off-by: Ricard Rosson <ricard@groundbits.com> Assisted-by: Claude (Anthropic Claude Code) Signed-off-by: Ricard Rosson <ricard@groundbits.com>
Apache NuttX is a real-time operating system (RTOS) with an emphasis on standards compliance and small footprint. Scalable from 8-bit to 64-bit microcontroller environments, the primary governing standards in NuttX are POSIX and ANSI standards. Additional standard APIs from Unix and other common RTOSs (such as VxWorks) are adopted for functionality not available under these standards, or for functionality that is not appropriate for deeply-embedded environments (such as fork()).
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